Tire pressure question

my68barracuda said
car is a 68 Barracuda
tires front 215/60/16 on 7 inch wide wheels
tires rear 225/60/16 on 8 inch wide wheels
the car is somewhat light weight, fiberglass hood and front bumper, aluminum front bumper brackets, light weight last year built slant. Carpet and interior trim is present, but no back seat, no under carpet sound deadening material.

The side wall of the tires says that max load capacity is at 51 psi.

Does a cold tire pressure on 38 psi seem about right?
The car rides and drives fine.
Thought I would ask to see what other folks run for tire pressure with non stock sized tires.

I would look at the original factory inflation pressure recommendation. Now over time tire construction and the size descriptions have changed. In '68 bias ply tires were the norm and imperial measurements used or a letter for width and a number for aspect ratio. Then they moved to bias belted tires to combat some of the bias tire squirm that cause.d wear. On these tires the second in row of ribs from each side wore more than the rest of the tread.
Then when radial ply construction was introduced on imported cars in the late '60s, the benefits became obvious. Longer tread life, better adhesion, better handling. Along with this came the metric size descriptor pretty much standard now.
Keep in mind that the max load tire pressure is what the tire carcass is capable of holding, not what the vehicle requires with that tire. A tire proffessional should be able to made an educated guess of the required pressure to run. Chalk across the tread as described elsewhere here or a temperature gun will be the best bet to fine tune from there. If the tire guy looks at the sidewall and tells you to run the max embossed on the sidewall, run. They are no proffessional. Another point on new vehicles, the engineers generally do a fine job of determining all the proper operating conditions. In todays world of Corporate Average Fuel Economy, running the tires hard with higher pressure lowers rolling resistance and increases the fuel mileage slightly. This gets them brownie points with the Feds 'n Heads, but the tires are most likely going to wear the centers. Get a tire wear guage and check the wear pattern monthly. You need to measure the center and both edges. Make sure not to measure on one of the treadwear indicators, a slightly raised point in the bottom of the grooves. Using this if you notice a different depth showing up you can adjust your pressures to keep the wear even.